There are several commercially available implantable medication delivery devices. Two such devices are provided by Medtronic, Inc. of Minneapolis, Minn. These include the Synchromed product as well as the MIP product. A propellant is utilized to maintain a constant absolute pressure at body temperature. The reservoir and the inlet side of the pump mechanism are at a constant absolute pressure while the tip of the output catheter and thus the outlet of the pump mechanism are at an ambient pressure. The ambient pressure may vary depending upon environmental conditions such as local barometric pressure and altitude, etc. Variations in temperature of the body in which the device is implanted may also affect the device. Because of the critical nature of such drug delivery systems, it always a desire to provide for a system with additional features.